Warm, moisture-laden air can exist in buildings even in buildings in colder climates. A significant amount of moisture can be placed into the air through common household activities, such as cooking, bathing and showering.
Especially in colder climates, insulation in a wall structure helps to reduce heat loss from buildings which are heated due to the cold climate. As moisture-laden air passes through the wall structure of such buildings, the moisture-laden air encounters steadily decreasing temperatures. As the air is cooled while moving from the interior of a wall structure to the exterior of the wall structure, the air can eventually reach its dew point and water vapor in the air condenses to form moisture. The result can be a moisture buildup in the wall structure.
Vapor barriers are commonly employed on the warm side of wall structures in order to prevent moisture-laden air from entering the wall structure. However, vapor barriers are not usually perfect. In a typical building, multiple penetrations of a vapor barrier can occur, e.g., from electrical and plumbing lines and from windows and doors.
If the exterior temperature is cold enough, the moisture existing in the wall structure could eventually turn to frost or ice and, thus, be prevented from draining from the wall structure, at least until the exterior temperature increases. When that happens, however, the moisture can still cause significant damage to the wall structure.
Several products exist to allow drainage of moisture from wall structures once the moisture has formed in the wall structure.
U.S. Pat. No. 3,654,765, Healy et al, Subterranean Wall Drain, discloses a subterranean wall drain unit including a drain pipe having openings therein and a longitudinally extending planar core defining channels normal to the pipe. A water pervious sheet material covers one face of the core and the openings in the pipe to form a filter therefore. The other face of the core may be covered with a plastic sheet or other vapor barrier.
U.S. Pat. No. 3,888,087, Bergsland, Foundation Wall Protective Sheet, discloses improvements in protective membranes or sheets for foundation walls. The sheets have regular courses of protrusions for spacing the sheet from the foundation wall and a porous backing for drainage outwardly of the sheet. The protrusions provide air channels between the protective sheet and the foundation for thermal insulation and for facilitating drying of the foundation wall. Small vertical ribs between the courses of the protrusions provide convenient water passages to take care of drainage water in the porous backing without interfering with the air spaces and incidentally providing bending vertical lines for more facile installation handling. Modifications of the sheet include transverse ribs at lower portions of the sheet to allow horizontal bending thereof wall for footing and drainage configurations. A barrier for preventing back fill falling between the protective sheathing and foundation is also disclosed.
U.S. Pat. No. 3,318,056, Thompson, Ventilating Wall Construction With Stud Location Indicators, discloses a sheet of building material placed between wall veneers for moisture protection that includes vertical drainage channels and perforations.
U.S. Pat. No. 6,298,620, Hatzinilolas, Moisture Control Panel, discloses a moisture control panel used in exterior walls. A wall constructed with the panel has an inner back-up wall component and an outer wall component of a moisture pervious material, for example, stucco. The moisture control panel is positioned between the two. It has a base sheet on the inner face of the outer wall component. A set of drying perforations slope downwardly toward the inside through this sheet. This drains moisture from the inside of the outer wall component. On the inside, the bay sheet has a set of upwardly sloping bosses which provide an air space on the inside the moisture control panel providing for air circulation and drainage of any moisture.
U.S. Pat. No. 4,381,630, Koester, Foundation Vent Structure, discloses a foundation vent structure positioned upon the footings of the building below the lowermost row of concrete blocks of the basement wall and extends below the concrete floor of the basement. The vent structure is formed of a plastic material, preferably in strips, and is shaped to define alternate tunnels and channels having openings therein. The vent structure intercommunicates the openings in the hollow, concrete blocks with the drain area located along the marginal area below the basement wall to permit moisture to be vented into this drain area.
However, significant problems exist with such pre-existing products and systems. Such products can prevent the continued movement of moisture of water vapor from the interior to the exterior side of the wall structure where the moisture or water vapor then exits the wall structure and, hence, can cause no further damage. Such products can also become contaminated with other construction materials being used in the formulation of the wall structure or otherwise in the construction of the building.